This invention relates in general to a method of ornamenting synthetic resin products and more in particular to a handle made of thermoplastic resin which is well adapted for use in a handle of a window glass regulator for vehicles and the like, and simulates the real or genuine metal handles of this type and which has a very splendid and attractive brightness in appearance.
It has been the practice in the art that most of the handles of this type have been made of zinc or zinc base alloy by the known die casting technique. Such zinc or zinc base alloy handle is characterized by a comparatively lighter nature and readiness for application of conventional plating technique. The plating is not only for the purpose of achieving a splendid and attractive bright appearance which is customarily demanded by a wider public but also to meet otherwise a requirement to have an occupant become aware of the location of the handle even though in dark circumstances within the vehicle particularly at night.
Due to cheaper and smaller weight of the synthetic resin handles, many substitutes for all metallic handles have been tried in the art, but none of the synthetic resin handles has been found to equal it for the special purpose herein described, that is for continuing ability to simulate the all metallic handles during the service life particularly with respect to a splendid and attractive brightness in appearance.
The special object of the invention therefore is the production of a thermoplastic resin handle which is as well suited to this purpose as the metallic handles in appearance.
A further object of the invention is the production of the thermoplastic resin door handle simulating the conventional metallic handle in appearance but having certain properties of the advantageous thermoplastic resin products particularly with a view to saving substantial manufacturing costs and decreasing the weight of the resulting handle and thereby rendering the resulting handle superior in this respect to the conventional all metallic handle.
Various method have been provided for the synthetic resin products in simulating the all metallic products in appearance by coating or ornamenting the synthetic resin products with a metallic film or sheet as described below.
1. affixing a thin gauge sheet metal to the surface of the synthetic resin products by means of some affixing material commercially available PA1 2. securing a thin gauge sheet metal by fitting to a contoured recess in the face of products to a closely similar contour of the sheet metal PA1 3. plating the synthetic resin products with melting metal of desired appearance. PA1 4. covering or coating the synthetic resin products with the sheet metal by means of the known inserting technique PA1 5. securing the sheet metal to the surface of the synthetic resin products by pressing it against the surface under a heated and softened or molten condition of the synthetic resin material
In actual use, the handle is required to have a certain strength against the load. For meeting such requirement, there has been usually preferred in the art the known polyacetal synthetic resin for forming the handle.
In actual test, none of the above mentioned five methods 1 to 5 has proven to be sufficient for the polyacetal resin products to be applied, even though they have been found applicable to various resins other than the polyacetal resin.
In detail, the above methods 3 and 5 have been found difficult in application to the polyacetal resin products, because of its peculiar properties.
The method 1 has proven to be inferior in durability, i.e., service life of the resultant products.
With the method 4, it is difficult to hold the metal sheet in the covering position when the method is applied.
The method 2 also has proven to be insufficient in the durability of the resultant products produced as is the products by the method 4. For freedom from such drawback, there will be required to apply some additional steps to the resultant product.